One arrangement for the electrical system of a conventional four-cycle engine is that where certain electrical system features are driven by a greatly extended end of a crankshaft of the engine. In this arrangement, the crankshaft has a first end and a second end, the second end extending outwardly of the engine in driving engagement with a drive shaft or similar feature. The first end of the crankshaft also extends from the engine. Normally, the first end of the crankshaft has a cam shaft drive member positioned thereon. The crankshaft extends further outwardly beyond the cam shaft drive member to drive a generator and/or one or more other electrical features of the engine which are positioned beyond the end of the engine about the crankshaft.
Alternatively, the flywheel is often positioned at the end of the engine on that portion of the crankshaft extending to the drive shaft. In this arrangement, the generator and/or other electrical system features may be provided within a flywheel chamber at end of the engine.
When a four-cycle engine is utilized in a watercraft application, problems arise with respect to the above-stated orientations of electrical components. These problems are due, in part, to the mounting of the engine vertically within an outboard motor cowling. In an outboard motor application, the engine is mounted so that the crankshaft extends generally vertically down from the engine to a drive a propeller.
So arranged, it is undesirable for the engine or its associated components to extend too far above the outboard motor's pivot point to the watercraft. If the engine is too tall, its center of gravity is high, making it more difficult to trim the outboard motor. As disclosed above, the first arrangement for the electrical components has the disadvantage that the engine has an excessive height because the generator and other features are positioned beyond the end of the engine for convenient driving by the greatly extended crankshaft. Another problem with the first arrangement disclosed above is that the crankshaft is quite expensive to manufacture, needing sufficient reinforcement to be of sufficient strength to support the components along its length.
The second arrangement disclosed above has the advantage that the generator and other electrical components are positioned lower in the motor. In an outboard motor setting, however, water invasion is an ever present hazard. In this arrangement where the electrical components such as the generator is positioned at the bottom end of the engine, they are subject to water damage if extensive sealing mechanisms are not employed. In addition, this second arrangement requires a ventilation mechanism to prevent damage to the components from heat generated by the engine.
A watercraft electrical system which provides for compact and convenient mounting of the electrical components is desirable.